Please help!! Worried about my baby boy!

S
My son is 1 year old, almost 13 months. At his one year doctor check up he had two shots, exactly one week later he started having diarrhea, now going on 6 days with it. It's bad but not all the time he could be fine all day then it hit at night or have it going on all day and be fine at night. Nothing new has been introduced into his diet so that's not it, it's not a bug or anything like that. Went to the Dr today and he didn't have any reasons on why it's happening. I've also looked up anything I could think of online. I just want my baby boy feeling better and I don't know how to help him. Does anyone have any advice please!? Feeling like a horrible mother since I can't help or figure out what's wrong 😭